usb: Add support to set autosuspend delay by controller driver

USB core driver sets the autosuspend delay to 1 sec for root hub and
its children by default. In case if delay needs to be changed for a
particular controller, it requires class driver to explicitly call
PM API to set the new values. Hence add a call back handler to set
autosuspend delay in controller driver. This makes class driver code
generic.

Change-Id: I62121651f0a9648a2909ca7eb4081a6c2567ed01
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>